The specific aims of the project are to examine the development of coordinated bimanual action in school age children and adolescents from 7- 22 years by cross-sectional design. Motor tasks of interlimb coordination were chosen to permit a comparison of major theoretical models of motor timing control and temporal organization: one of the tasks involves bimanual finger tapping of patterns of increasing complexity as the prescribed response frequency is varied. The other requires subjects to rotate both arms concurrently to track a prescribed path in either the mirror image or parallel bode with and without visual feedback and to rotate the arms at various rates of angular velocity. The programs of data collection and data analysis are designed to examine the development of bimanual motor performance, as well as the processes of motor coordination in terms of relative phasing, and spontaneous phase shifts as the response velocity is systematically varied. The long term objectives of the normative studies are to formulate a theoretically informed research strategy for investigating the development of motor coordination in children and adolescents with developmental disabilities.